When a patient is unable to adequately breathe independently, an external mechanical ventilator may be used to provide temporary or permanent breathing support. The ventilator pumps air into and out of the subject's lungs such as, for example, though an endotracheal (ET) or other tracheal tube. In one example, a distal portion of the tracheal tube is introduced into the subject's trachea (windpipe) through an incision made in the subject's throat. A proximal portion of the tracheal tube is connected to the ventilator. An inflatable cuff near the distal end of the tracheal tube is inflated to completely occupy the intratracheal region surrounding the tracheal tube. This creates a seal that prevents airflow through the trachea other than through the tracheal tube, so that the ventilator can provide the subject with breathing support through the tracheal tube. In another example, the tracheal tube is inserted via the subject's mouth, rather than into an incision in the subject's throat.
However, normal lungs continuously secrete mucus that is sticky enough to trap foreign particles. In the absence of the ventilator and tracheal tube, such secreted mucus would be carried up the windpipe to the throat by the action of cilia, such that the patient may then swallow the mucus. When damage or disease disables this mechanism, or reduces its ability to move the required volume of mucus, there exists a risk of the lungs drowning in fluid. In addition, certain medical procedures may disrupt such normal mucus transport. For example, the inflatable cuff at the distal end of a tracheal tube inserted into a person on a ventilator will block the normal flow of the lung-cleansing mucus.
One technique for removing accumulated fluid from the lungs includes interrupting the patient's ventilation by disconnecting the proximal end of the tracheal tube from the ventilator. A suction tube is then inserted through the tracheal tube beyond the cuff at its distal end. By applying an airflow-creating vacuum to the proximal end of the suction tube, fluid is removed from the lungs. However, such an airflow-creating vacuum has a limited capability to lift fluid through a small diameter tube against the force of gravity, to remove the fluid from the lungs. Moreover, this procedure must be repeated often enough (e.g., every 0.25 to 8 hours). Otherwise, the mucus may accumulate or dry, which, in turn, may make its removal more difficult. Each occurrence of such airflow suctioning interrupts the breathing assistance provided by the ventilator. Moreover, such airflow suctioning risks damage to the windpipe walls. It also creates a risk of infection to both the patient and the caregiver, who may come in contact with the extracted fluids or the air used to suction the fluid. The risk of infection is exacerbated because the suction tube is typically re-used despite its contamination and direct connection to a waste container that stores the suctioned fluid. Moreover, frequent intervention by a caregiver is aggravating to the patient, and may cause considerable resulting anxiety. Such frequent intervention by a caregiver is also costly. In addition, the caregiver must be well-trained to reduce the risks of damage or infection presented by such repeated suctioning. Among other things, the present inventors have recognized that continuous airflow-assisted suctioning, however, would likely interfere with the patient's breathing because of the airflow required to vacuum the fluid from the lungs. For these and other reasons, the present inventors have recognized an unmet need for improved fluid transportation techniques, such as for removing mucus from a patient's lungs that are being mechanically ventilated, or for otherwise removing bodily fluids from a patient.